The Stockdale Group is a

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

lithostratigraphic Lithostratigraphy is a sub-discipline of stratigraphy, the geology, geological science associated with the study of stratum, strata or rock layers. Major focuses include geochronology, comparative geology, and petrology. In general, strata are ...

group A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic iden ...

(a sequence of

rock strata In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ei ...

) in the southern

Lake District The Lake District, also known as the Lakes or Lakeland, is a mountainous region in North West England. A popular holiday destination, it is famous for its lakes, forests, and mountains (or ''fells''), and its associations with William Wordswor ...

and

Howgill Fells The Howgill Fells are uplands in Northern England between the Lake District and the Yorkshire Dales, lying roughly within a triangle formed by the towns of Sedbergh and Kirkby Stephen and the village of Tebay.

of the

Pennines The Pennines (), also known as the Pennine Chain or Pennine Hills, are a range of uplands running between three regions of Northern England: North West England on the west, North East England and Yorkshire and the Humber on the east. Commo ...

of northern

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

. The name is derived from the locality of Stockdale near the top of

Longsleddale Longsleddale () is a valley and civil parish in the South Lakeland district of the English county of Cumbria. It includes the hamlet of Sadgill. The parish has a population of 73. As the population taken at the 2011 Census was less than 100, deta ...

Cumbria Cumbria ( ) is a ceremonial and non-metropolitan county in North West England, bordering Scotland. The county and Cumbria County Council, its local government, came into existence in 1974 after the passage of the Local Government Act 1972. Cumb ...

. It is included within the

Windermere Supergroup The Windermere Supergroup is a geological unit formed during the Ordovician to Silurian periods ~, and exposed in northwest England, including the Pennines and correlates along its strike, in the Isle of Man and Ireland, and down-dip in the South ...

. The rocks of the Group have also previously been referred to as the Stockdale Shales or Stockdale Subgroup. The group comprises

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

s and

oolite Oolite or oölite (''egg stone'') is a sedimentary rock formed from ooids, spherical grains composed of concentric layers. The name derives from the Ancient Greek word for egg (ᾠόν). Strictly, oolites consist of ooids of diameter 0.25–2 ...

s and some

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

s and

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

s which reach a maximum thickness of 120m in the area. It is divided into a lower Skelgill Formation which is overlain by an upper Browgill Formation.

References

* {{Refend Silurian System of Europe Geology of England Geological groups of the United Kingdom Geologic formations of the United Kingdom